Aftertreating isocyanate-modified cellulosic fibers with dimethyl sulfoxide, pyridine or dimethyl formamide



United States Patent 3,350,163 AFTERTREATING ISOCYANATE-MODIFIED CEL- LULOSIC F BER WITH DIMETIHYL SULFOXIDE, PYRIDINE 0R DIMETHYL FORMAMIDE Charles H.-Mack and Samuel Ellzey, Jr., New Orleans,

La., assignors to the United States of America as represented .by the Secretary of Agriculture N0 Drawing. Filed June 17, 1965, Ser. No. 464,877 5 Claims. (Cl. 8-1-16) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted :to the Government .of the United States of America.

This invention relates to a process for the improvement of strength of cotton yarns and more particularly to a process for the improvement of strength of chemically modified cotton yarns.

The search for novel methods to improve the strength of cotton yarns and fabrics, more specifically the strength of chemically modified cotton yarns and fabrics, is a continuing one. More often than not it has been found that the chemical modification of cotton cellulose imparts to the said cotton cellulose a reduction in tensile strength. The said reduction in tensile strength is generally attributable to either acid or thermal .degradation of the fibrous cellulose. Furthermore the damage which is caused is permanent and any improvement in strength by the addition of lubricants or softeners is usually temporary since these are removed by either laundering or drycleaning. The usefulness of a process for the improvement of strength of cotton fibers, yarns, or fabrics is obvious to one skilled in the art.

The object of this invention is to describe a process for increasing tensile strength of chemically modified cotton yarns.

The process for improving the tensile strength of chemically modified cotton yarn consists generally of swelling the said chemically modified cotton yarn with a suitable swelling agent, applying tension to the swelled yarn, and removing the solvent while the yarn is still under tension.

The swelling agent used will depend upon the type of chemical modification on the cotton yarn. For example, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and pyridine are good swelling agents for cotton yarn modified with aryl monoisocyanates. The degree of tensile strength improvement depends upon the degree of swelling obtained.

The temperature range in which the modified yarn is swelled extends from the freezing point to the boiling point of the solvent, although ambient or room temperature is the preferred temperature. For example, the range for pyridine is from -42 C. to 115 C. demonstrating the wide range of swelling temperatures which are operable. It is obvious to one skilled in the art that lower temperatures favor greater swelling.

The contact time between the modified cotton yarn and the swelling solvent is not critical as maximum swelling is attained in a matter of seconds. The normal swelling time of one minute is preferred.

The tension applied to the swelled yarn is not critical as will be seen from the examples. In general, the limits of tension required are between 10% and 100% of the breaking strength of the swelled yarn. The application of a tension of of the breaking load of the swelled yarn is preferred.

With the tension still applied, the swelling agent is removed by any convenient means, such as evaporation, washing and the like. Removal of the swelling agent by washing with a solvent which is either water or a solvent miscible with water is preferred.

Yarn suitable for use in this invention is limited to those made of cellulosic fibers. Preferred yarn is that made of either cotton or rayon.

Since the swelled yarn is in a plastic state and there is a load applied to the yarn, there is usually an accompanying increase in the length of the yarn. This is an advantage in that the yarn has a higher yarn number .(a measure of linear density) together with increased strength.

The following examples are given by way of illustration and should not be construed as limiting the scope of this invention.

E mp 1 A 10 ft. length of scoured and bleached 7.0/2 mercerized cotton sewing thread (having a breaking strength of 336.1 grams and an elongation at break of 4.18%) which had been treated with phenyl isocyanate to a d gree of substitution (D8) of 0.83 (treated yarn had a breaking strength of 250.2 grams and elongation at break of 23.88%) was immersed .in N,N-.dirnethyl formamide (DMF) and allowed to swell .for about one minute. Both ends of the swelled yarn were tied to a 5.0 gram weight and the folded yarn looped over a lubricated glass rod, care being taken so that the load was evenly distributed between both halves of the length of the yarn employed, that is, 25 grams tension for each half. The tension on the swelled yarn increased the length about 10% of normal length. After about one minute, while the tension was still applied, a stream of water was directed on the yarn to remove the DMF. At the same time the yarn changed from a soft translucent state to normal cotton yarn appearance. The yarn was then allowed to air dry. Breaking strength for this yarn was 445.2 grams and elongation at break was 2.94%. The breaking strength and percent elongation at break of the unmodified yarn which had been given the same treatment with DMF was 328.9 grams and 4.05%, respectively.

Example 2 Experimental conditions were the same as in Example 1 1 except that a IOU-gram weight was used representing a SO-gram tension on the yarn. The breaking strength of the tension-treated yarn was 446.4 grams and the elongation at break was 3.44%.

Example 3 Experimental conditions were the same as in Example except that a 25-gram weight was used representing 12.5 grams tension on each half of the length of the yarn employed. The breaking strength of the tension-treated yarn was 458.3 grams and elongation at break was 3.61%.

Example 4 Experimental conditions were the same as in Example 1 except that dimethyl sulfoxide (DMSO) was used as the swelling agent instead of DMF. The breaking strength of the tension-treated yarn was 431.9 grams and elongation at break 3.06%.

Example 5 Experimental conditions were the same as in Example 1 except that pyridine was used as the swelling agent instead of DMF. The breaking strength of the tensiontreated yarn was 379.4 grams and elongation at break was 2.65%.

Example 6 Experimental conditions were the same as in Example 1 except that a p-methoxyphenyl isocyanate treated yarn (DS, 1.10; breaking strength, 149:6 grams; elongation at break, 21.12%) was used instead of phenyl isocyanate treated yarn. The breaking strength of the tension-treated yarn was 30711 grams and elongation at break was 2.68%.

3 Example 7 Experimental conditions were the same as in Example 1 except that p-bromophenyl isocyanate treated yarn (DS, 0.34; breaking strength, 362.0 grams; elongation at break, 6.41%) was used instead of phenyl isocyanate treated yarn. The breaking strength of the tension-treated yarn was 384.0 grams and elongation at break was 5.78%.

Example 8 Experimental conditions were the same as in Example 1 except that a-naphthyl isocyanate treated yarn (DS, 0.63; breaking strength, 172.6 grams; elongation at break, 9.73%) was used instead of phenyl isocyanate treated yarn. The breaking strength of the tension-treated yarn was 335.5 grams 'and elongation at break was 2.89%.

We claim:

1. A process for treating cellulosic yarn which has been chemically modified with an aryl isocyanate comprising:

(a) wetting the chemically modified cellulosic yarn with a swelling agent selected from the group consisting of N,N-dimethylformamide, pyridine, and dimethyl sulfoxide,

(b) applying tension less than that required to break the yarn, to the wetted and swollen chemically modified cellulosic yarn, and

() Washing the said swelling agent from the said swollen chemically modified cellulosic yarn with a solvent, while the swollen chemically modified cellulosic yarn is maintained under tension.

2. A process for treating cellulosic yarn which has been chemically modified with an aryl isocyanate to a degree of substitution of about from 0.34 to 1.10 comprising:

(a) wetting the chemically modified cellulosic yarn with a swelling agent selected from the group consisting of N,N-dimethylformamide, pyridine, and dimethyl sulfoxide,

(b) applying tension less than that required to break the yarn, to the wetted and swollen chemically modified cellulosic yarn, and

(c) washing the said swelling agent from the said swollen chemically modified cellulosic yarn with a solvent while the swollen chemically modified cellulosic yarn is maintained under tension.

3. The process of claim 2 wherein the swelling agent is N,N-dimethylformamide.

4. The process of claim 2 wherein the swelling agent is pyridine.

5. The process of claim 2 wherein the swelling agent is dimethyl sulfoxide.

References Cited UNITED STATES PATENTS 3,007,763 11/1961 Adams -81l6.2

NORMAN G. T-ORCHIN, Primary Examiner.

J. C. CANNON, Assistant Examiner. 

1. A PROCESS FOR TREATING CELLULOSIC YARN WHICH HAS BEEN CHEMICALLY MODIFIED WITH AN ARYL ISOCYAMATE COMPRISING: (A) WETTING THE CHEMICALLY MODIFIED CELLULOSIC YARN WITH A SWELLING AGENT SELECTED FROM THE GROUP CONSISTING OF N,N-DIMETHYLFORMANIDE, PYRIDINE, AND DIMETHYL SULFOXIDE, (B) APPLYING TENSION LESS THAN THAT REQUIRED TO BREAK THE YARN, TO THE WETTED AND SWOLLEN CHEMICALLY MODIFIED CELLULOSIC YARN, AND (C) WASHING THE SAID SWELLING AGENT FROM SAID SWOLLEN CHEMICALLY MODIFIED CELULOSIC YARN WITH A SOLVENT, WHILE THE SWOLLEN CHEMICALLY MODIFIED CELLULOSIC YARN IS MAINTAINED UNDER TENSION. 